<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>01_JS的三种引入方式</title>
    <script src="01.js">
        //不可以写代码，写了也不会生效
        console.log("2222")
    </script>
</head>
<body>
    <button onclick="alert('请先登录')">点击即玩</button>
    <button onclick="console.log('点点点')">点</button>

    <h1 id="aaa">一级标题</h1>
    <script>
        console.log("执行");
        console.log(aaa);
    </script>
</body>
</html>